Primordial black holes

Did the Big Bang fill the Universe with microscopic black holes? Primordial Black Holes (PBHs) are exceptional astrophysical objects, where both gravitational and quantum conditions are extreme. They are just little, tiny black holes! PBHs are very different from huge core-collapse black holes, which have masses larger than the Sun, and form from dying stars: a typical PBH might have a mass of 10^14 grams (a few times the mass of Mount Everest), and would have formed from density fluctuations in the very early universe.

black hole world-sheet schematic, (c)NASA Studying PBHs could probe a new era in general relativity, and open a fascinating window on the state of our Universe just at the end of inflation. As their masses could be very small (down to the Planck scale ~ 10^{-5}g ), the gravitational field at horizon should be incredibly high, and they should undergo a very intense Hawking evaporation mechanism. By this process, the PBH will emit all the possible elementary particles, including quarks and gluons that fragment into hadrons, contributing to the cosmic-ray population. In particular, PBH evaporation would contribute an unusual population of low-energy antiprotons and antideuterons. AMS is poised to discover, or establish strong upper limits on, these particular cosmic rays - in particular the antideuterons, which may be the best way of spotting PBHs.

This gives invaluable information on the state of the very early universe (especially in the framework of inflationary cosmology) probing the fluctuations on scales that no other observational means can investigate. It could lead to a real breakthrough in both cosmology and fundamental physics.


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